package com.ftg.learn.chapter18;

import java.time.LocalDate;
import java.time.temporal.ChronoUnit;
import java.util.Hashtable;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;

/**
 * @author KangJx
 * @date 2021/8/24
 */
public class TestDate {

    public static void main(String[] args) throws InterruptedException {
        String a = null;
        String b = "";

        Optional<String> op = Optional.empty();
        System.out.println(op.isPresent());

        System.out.println(Optional.ofNullable(a));
        System.out.println(Optional.ofNullable(b));
    }
}
